This invention relates to a container emptying apparatus and method. The apparatus and method has particular application for a dock level dumper of the type which, for example, may be used to empty rather large wheel-mounted containers into a trash compactor or a trailer parked adjacent the dock. A typical construction for such a container is a plastic body having a bottom and four side walls. One of the walls comprises a front wall which is angled forward to assist in emptying. The container is mounted on a pair of relatively large wheels positioned near the front of the bottom and a relatively small pair of caster wheels mounted near the rear of the bottom.
Since such containers are relatively deep, the container must be nearly inverted in order to insure that the contents are completely emptied. In addition, it is helpful if the container can be gently jarred near the end of the emptying movement to shake loose the contents and further insure complete emptying.
Prior art emptying devices typically grip the container at or near its front wall while supporting the front wall. The container is then lifted and tipped while supporting the front wall of the container. See, for example, U.S. Pat. No. 4,285,624 (FIG. 8). This type of emptying motion requires that the container be lifted quite high off of the floor and swung through a wide and high arc around a single pivot. This motion is quite inefficient and places stress on the container since the container is pivoted around the same point even as the center of gravity of the container changes. In addition, the emptying takes place when the container is high above the receptacle, increasing the force with which the contents are emptied and increasing the possibility that the contents of the container will miss the receptacle altogether.
For safety reasons, it would also be desirable to provide a positive means for insuring that the container is properly mounted on the emptying apparatus before lifting begins.
The invention described below provides a compact, efficient and safe emptying apparatus which nevertheless provides complete emptying with minimum wear and tear on the container. In addition, safety features prevent premature lifting or lifting when the cart is not properly mounted on the lifter.